Cooling system for internal combustion engines



Nov. 13, 1934. F. LJUNGSTROM COOLING SYSTEM FOR INTERNAL COMBUSTIONENGINES 4 Sheets-Shet 1 Filed March 1'7. 1933 Nov. 13, 1934. F.LJUNGSTROM COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed March17, 1933 4 Sheets-Sheet 2 Nov. 13, 1934. F. LJUNGSTROM 1,980,811

COOLING SYSTEM FOR INTERNAL COMBUSTION ENGINES Filed March 17, 1933 4Sheets-.Sheet 5 7 {1; ATTORNEY Nov. 13, 1934. F. LJUNGSTROM COOLINGSYSTEM FOR INTERNAL COMBUSTION ENGINES I Filed March 17. 1933 4Sheets-Sheet 4 INVE TOR g FW-m? Patented Nov. 13, 1934 UNITED STATESCOOLING SYSTEM FOR INTERNAL COMBUSTION ENGINES Fredrik Ljungstriim,Lidingo, Sweden, assignor to Aktiebolaget Spontan, corporation of SwedenStockholm, Sweden, a

Application March 17, 1933, Serial No. 661,251 In Germany June 20, 193237 Claims.

The present invention relates to cooling systems for internal combustionengines and has particular reference to cooling systems of the typeadapted to utilize a cooling fluid of high boiling point and lowfreezing point, such as oil, which is circulated in a closed path offlow in which it absorbs heat from the parts of the engine to be cooledand dissipates this heat in a cooler or radiator over which cooling airis passed.

The usual cooling systems employing water as a cooling medium aresubject to numerous disadvantages such as freezing at low temperaturesand evaporation of the water at high temperatures, while, on the otherhand, oil and like fluids of high boiling point and low freezing pointnot only avoid such disadvantages but provide other distinct advantages,such, for example, as that of permitting the engine to be operated at ahigher temperature and consequently with 20 greater efliciency than ispossible with water cooling.

Heretofore, however, in spite of the known advantages of oil and likefluids for cooling purposes, systems employing such fluids have not beensuccessful, due largely to the high viscosity and low specific heat withconsequent low heat conductivity of oil as compared with water.

The present invention has for a principal object the provision of animproved cooling system adapted to employ oil as a cooling medium. Morespecifically, the invention contemplates the provision of novel radiatorstructure with the cooling fan and circulating pump elements of a systemof the character under discussion, by means of which novel structureeflicient cooling may be obtained and practical advantages with respectto compactness and ruggedness of design, simplicity and low cost, besecured, as will hereinafter more fully appear in conjunction with theensuing description of suitable examples of apparatus for carrying theinvention into effect.

In the accompanying drawings forming a part of this specification andillustrative of the examples of apparatus to be described:

Fig. 1 is a horizontal cross-section of the principal elements of acooling system according to the present invention as applied to anautomobile or like engine;

Fig. 2 is a section taken on the line 22 of Fig. 1;

Fig. 3 is a section taken on the line 33 of Fig. 1;

Fig. 4 is a front elevation, on a reduced scale, of the right hand halfof the fan and radiator. shown in Fig. 1;

Fig. 5 is a more or less diagrammatic illustration, on a still furtherreduced scale, of one form of radiator tube, in elevation;

Fig. 6 is a view similar to Fig. '5 and taken at right angles thereto;

Fig. 7 is an enlarged longitudinal cross-section of a portion of oneform of tube;

Fig. 7a is a cross-section of the tube shown in F 7;

Fig. 8 is a side elevation of a portion of one form of radiator tube;

Fig. 8a is a view taken at right angles to Fig. 8;

Fig. 8b is a cross-section taken on the line 8b8b of Fig. 8; i

Fig. 9 is a front elevation showing a portion of another form ofradiator;

Fig. 10 is a longitudinal section of the part of the radiator shown inFig. 9;

Fig. 10a is a section taken on the line 10a-10a of Fig. 10;

Fig. 11 is a more or less diagrammatic front elevation of a part of aradiator employing still another form of tube;

Fig. 11a is a perspective view of one of the tubes shown in Fig. 11;

Figs. 12 to 19 inclusive show the several steps employed in making stillanother form of radiator tube;

Fig. 20 is a front elevation, partly in section, of a radiator havingtubes of the form shown in Figs. 12 to 19;

Fig. 21 is an axial section of the structure shown in Fig. 20;

Fig. 22 is a plan view of part of the radiator shown in Fig. 20;

Fig. 23 is an axial section of an aviation engine having a coolingsystem embodying the invention, and

Fig. 24 is a section taken on the line 24-24 of Fig. 23.

Turning now more particularly to Figs. 1 to 4 of the drawings, referencenumeral 10 indicates one end of a cylinder block of an internalcombustion engine having one or more cylinders, one being indicated at12, jacketed to provide spaces for circulation of cooling fluid. As usedherein the term cylinder block isintended to include the cylinder blockstructure generally which includes the cylinder head portion of thestructure in the case of engines having cylinder heads separable fromthe main block structure in which the barrel portions of the cylindersare located. At the end or the cylinder block there are provided flanges14 and 16 having passages 18 and 20, respectively, for flow of coolingfluid to and from the jacket spaces in the cylinder block. The specificconstruction and arrangement of the cylinder block for providing thespaces for cooling fluid form no part of the present invention, but inconjunction with the use of oil or the like for cooling fluid, I preferto use a form of construction such as that disclosed in my copendingapplication, Serial No. 661,250 filed March 1'7, 1933.

The radiator of the cooling system is of the closed or surface type andcomprises a casing 22 in the form of a body of revolution, preferablycircular in cross-section and providing two central chambers 24 and 26,chamber 24 being an inlet chamber for receiving heated cooling fluidfrom the engine and for distributing this fluid to the cooling tubes ofthe radiator and chamber 26 being a collecting chamber for receivingcooled fluid from the tubes. Chambers 24 and 26 constitute headersconnected by a plurality of bent cooling tubes 28 which extend outwardlyfrom the central casing 22. The form and arrangement of these tubesconstitutes an important feature of the invention and will be describedin detail later.

Casing 22 is closed at one end by a member 30 which comprises arms 32and 34 cored to provide passages 36 and 38, the passage 36 providing aninlet conduit for conducting cooling fluid from the passage 18 to theinlet chamber 24 and passage 38 providing an outlet conduit connectingthe outlet chamber 26 of the radiator with the passage 20.

The opposite side of casing 22 is closed by a casing member 40. Members30 and 40 have central aligned passages therethrough and mounted in saidmembers by means of ball bearings 42 and 44 is a shaft 46 which projectsat each end through the casing. Shaft 46 is packed against leakage pastmember 40 by means of a stufling box comprising packing 48 compressed byspring 50 around the shaft between the packing and bearing 44 andleakage around the other end of the shaft past member 30 is prevented bya similar stufling box comprising packing 52 compressed by spring 54.

Chambers 24 and 26 are separated axially by means of a web 56 andchamber 24 is divided into an inner chamber 24a and an outer chamber 24bby means of a circular web or flange 58 which is advantageously formedas a part of member 40.

Fixed to shaft 46 in chamber 24a is the pump for circulating coolingfluid through the system. In the form shown, the circulating'pumpcomprises an impeller member 60 of the centrifugal type having a ring ofimpeller blades 62. Radially outside of the discharge ends of theimpeller blades 62, the flange 58 carries a ring of diflusor blades 64,the passages between these blades providing communication between theportions 24a and 24b of the inlet chamber. One or more by-pass openings66 provide for relatively restricted communication between chamber 24band chamber 26.

The end of shaft 46 projecting through member 40 has secured thereto thehub 68 of the cooling fan 70, which preferably comprises a relativelylarge number of radially extending blades 72.

The opposite projecting end of shaft 46 has secured thereto the pulley74 adapted to be driven by belt 76.

In case the engine is used in an automobile or like automotive vehicle,the unitary assembly comprising the radiator, circulating pump and fanis mounted at the forward end of the en gine and belt 76 may be readilydriven from a pulley (not shown) on the forward end of the engine crankshaft, in the usual manner. The two arms or branches 32 and 34 of member30 are preferably flanged as shown at 78 in Fig. 2 and removablysecured, respectively, to flanges 14 and 16 on the cylinder block bymeans of studs 80.

It will be observed that the assembly comprising all of the majorelements of the cooling system, other than the engine jackets, forms aselfcontained unit which is supported from the cylinder block by meansof the inlet and outlet conduits connecting the radiator with thecylinder block and readily removable from the engine as a unit, uponremoval of the studs 80.

The cooling tubes 28 in the present embodiment, as shown in Figs. 1 and4 to 6, comprise two sets or series of tubes 28a and 28b, the latter setbeing arranged outside of the former and both sets comprising tubes, oneend of which communicates with chamber 24b and the other end of whichcommunicates with chamber 26. The preferred shape of these tubes isshown more clearly in Figs. 5 and 6, the former showing a single tube infrontal elevation and Fig. 6 showing the same tube in side elevation.

As indicated in Fig. 5, the tube is preferably bent so as to provide-twoend portions a connected by curved intermediatev portions 5 to a middlecurved portion 0. Portions a are bent so that ends of the tube join thecasing 22 radially and the sections b are curved to involute form.Section 0 is preferably arcuate. As indicated in Fig. 6, the connectedsections a and b form two legs 25 and 2'7 situated in planes normal tothe axis of shaft 46, which may be considered as the axis of theradiator, and spaced apart axially of the radiator. These legs areconnected by the arcuate portion 0 of the tube which lies in a planeoblique with respect to the axis of the radiator.

As will be evident from Fig. 5, each of the tubes provides a loop havingrelatively closely adjacent ends and, as shown in Fig. 4, the severalloops in each set are uniformly spaced peripherally of the radiator.

Due to the bending of the sections b of the tubes to the form ofinvolutes, the distance between adjacent tubes in the same set ismaintained constant between the radially inner portions of the tubes andthe radially outer portions thereof, and this arrangement, as is clearlyillustrated in Fig. 4, provides for spaces of uniform area between thetubes for flow of cooling air.

Furthermore, as shown in Fig. 4, the ends of tubes in axially adjacenttransverse planes and lying in the same axial plane are bent outwardlyfrom the casing 22 in opposite directions so that the tubes in adjacentplanes cross each other as viewed in Fig. 4, that is, frontally of theradiator.

The tubes 28 are preferably of steel having relatively thin wallthickness and are, as shown in Fig. 1, preferably secured at their endsto the casing 22 by rolling the ends into suitable openings formed inthe casing wall.

The operation of the cooling system just described is largely obviousfrom the drawings. Assuming the system to be filled with a suitablecooling fluid, actuation of the shaft 46 from the crank shaft of theengine or other suitable source of power causes operation of the pump 60which draws cooling fluid from the engine block through the inletconduit 36 and delivers it through the diflusors 64 to the chamber 24bfrom which it passes through the cooling tubes, giving up its heatduring its passage through these tubes to the air which is forced overthe tubes by fan '70 which is simultaneously operated upon actuation ofshaft 46. The cooled fluid is returned to chamber 26 and from thischamber passes by way of the outlet conduit 38 to the cooling jackets ofthe engine where it again absorbs heat and is again withdrawn throughconduit 36 by pump 60, thus completing the cycle of circulation.

In this connection, it is desired to point out that lubricating oil ofthe same character as that used to lubricate the working parts of theengine is a desirable medium to use as cooling fluid since the use ofsuch oil provides numerous advantages. In the first place, fluid tightconstruction of the means forming the jacket spaces in the engine is notrequired, since leakage of a portion of the oil used for coolingpurposes into the crank case or other parts of the engine containinglubricating oil is not harmful and the cooling fluid in the coolingsystem may readily be maintained under pressure, which is desirable in aclosed circuit oil cooling system to prevent formation of gas due toheating of the oil to comparatively high temperatures, byinterconnecting the cooling system with the pressure side of the pumpfor circulating lubricating oil through the engine. Also, thisinterconnection may be employed to maintain the cooling system filledwith cooling fluid, replacing any fluid which may leak from the coolingcircuit. An arrangement suitable for utilizing lubricating oil as thecooling medium and for maintaining the cooling system under pressure andfor automatically replacing fluid lost from the system due to leakage isdisclosed in my copending application Serial No. 513,335. Obviously,other suitable means may be employed for maintaining the cooling circuitfllled with cooling fluid under pressure and for replacing fluid lostfrom the system due to leakage.

I have found that the placing of the ring of diffusor blades between thechamber in which the circulating pump works and the inlet ends of thecooling tubes increases the efliciency of operation of the system and Ihave further found and regard as important the provision of the bypassopening between the inlet and outlet chambers of the radiator. Thislatter is particularly important when oil or other cooling fluid havingthe viscosity characteristics of ordinary lubricating oil is used,especially under cold starting conditions. Assuming the system to befilled with lubricating oil and that the engine is started at lowtemperature, it will be evident that the comparatively long passagesthrough the cooling tubes will provide considerable resistance to flowof the oil which is comparatively viscous under the conditions assumed.Consequently, there will be a considerable flow of oil through thebypass opening, since, due to the comparatively short length of theby-pass passage, the resistance to flow therethrough is not materiallygreater under ,cold starting conditions than under normal runningconditions. Thus, in starting, an initial bypass flow is establishedwhich enables circulation to be set up immediately and which permitscomparatively rapid warming up of a portion of the I oil in the system.This in turn gradually causes heating of the radiator structure and ofthe oil in the tubes, with consequent lowering of viscosity of the oilin the tubes and diminished resistance to flow therethrough. As the oilbecomes warmer and less viscous, the resistance to flow through thecooling tubes becomes materially less than under the coldstarting-conditions, while theresistance to flow through thecomparatively short by-pass passage remains relatively constant andnormal circulation through the cooling tubes is gradually established asthe system warms up.

Due to the form and arrangement of the cooling tubes in the radiator,substantially uniform spaces for flow of cooling air over the tubes areprovided which aids in the uniformity of cooling and, due to the.oppositely curved arrangement of the legs of the tubes in adjacentplanes, the turbulence of flow of air over the tubes is enhanced, whichcontributes to maximum rate of heat transfer from the tubes to the airpassing thereover. Also, in the arrangement disclosed, the rapidity ofthe rate of heat transfer is enhanced because of the placing of thecooling tubes of the radiator on the discharge side of the cooling fanwhere the flow of air is more turbulent in character than is the flow ofair on the suction side of the fan which comprises the usual locationfor radiators of the character under discussion.

By employing the arrangement described, heat transfer at substantiallymaximum rate is obtained over the entire area of cooling surface and asa consequence a given cooling capacity may be obtained with a minimumamount of cooling surface, which is provided, in the constructionaccording to the present invention, by structure which is compact andrelatively rugged as compared with the usual cellular radiator and whichcan be manufactured at relatively low cost.

It is further to be noted that by forming the cooling tubes asdescribed, the resulting radiator structure is in the form of a body ofrevolution or circular in frontal area and air is forced oversubstantially the entire frontal area of the radiator directly from theblades of the cooling fan, which preferably, as shown, has a diametersubstantially the same as that of the radiator.

While the invention is not limited to this specific form of radiator,the general form of radiator shown is to be preferred.

In the case of the ordinary cooling system employing water as a coolingfluid, a high rate of heat transfer is obtained between the water andthe inside surface of the cooling elements of the radiator as comparedwith the rate of heat transfer from the outer surfaces of the radiatorto the air passing thereover. For this reason it is customary toincrease the outside area of radiators by the use of fins, flanges, andthe like.

On the other hand, when oil is used as the cooling fluid, the rate ofheat transfer from the oil to the inside surfaces of the radiatorcooling elements is relatively lower compared to the rate of heattransfer from the external radiator surfaces to the air, due to therelatively higher viscosity and lower specific heat of oil as comparedwith water. Therefore, if in the case of oil cooling systems, aconventional type of radiator with extended external cooling surfaceswere employed, the radiator would operate normally at a temperature notmuch above that of the cooling air. This in turn would lead to theformation of a relatively cold and viscous oil film on the insidesurfaces of the radiator, so that transfer of heat to the walls of theradiator would be greatly reduced because of the relatively highviscosity of the oil at the low temperature.

This difl'iculty with respect to heat transmission to the walls of theradiator from the oil is avoided in accordance with the presentinvention by utilizing a radiator construction in which the internal andexternal areas for the transmission of heat are of about equal size. Itwill be apparent that in the radiator illustrated in Figs. 1 and 3, theplain tubes provide inside and outside heat transfer surfaces ofsubstantially equal area. With this arrangement the greatest resistanceto transfer of heat is between the outside surfaces of the tubes and theair, and as a result the cooling tubes operate normally at a temperatureconsiderably above that of the surrounding air and approaching that ofthe oil circulated therethrough. This relatively high operatingtemperature of the tubes prevents the formation of a cold and relativelyviscous oil film on the inner surfaces of the tubes so that a relativelygood rate of heat transfer is obtained between the oil and the tubes. Itis for this reason that, when oil is used as a cooling medium, plainsteel tubes having relatively thin walls provide the most satisfactoryconstruction.

1 In some cases it may be advantageous to in crease the rate of heattransfer between the cooling fluid and the inside surfaces of thecooling tubes. This may be accomplished most advantageously by meanswhich tend to increase the turbulence of flow of the cooling fluidpassing through the cooling tubes. By way of example, there is shown inFigs. 7 and 7a means for creating turbulence of flow comprising acorrugated strip 82 of thin sheet metal inserted in a cooling tube 28.

Figs. 8, 8a and 8b illustrate another means for creating tubulence offlow comprising a cooling tube which at intervals along its length isflattened as at 84 so as to provide more or less regularly spacedportions of oval or elliptical crosssection as shown in Fig. 8b.

It will be evident that many different sectional forms of cooling tubesmay be employed and that the specific shape of the tubes may be variedwithin the scope of the invention. In Figs. 9, 10 and 10a is illustrateda cooling tube arrangement similar to the arrangement shown in Fig. 4.In this arrangement, the cooling tubes 28' throughout their length,except for the end portions where they are rolled into the casing 22,are flattened to elliptical form in cross-section as shown in Fig. 10a,the major axis of the crosssectional area of the tubes being axial sothat the tubes present the least resistance to flow of air axially pastthe radiator. With this arrangement the ratio of the area of coolingsurface to the cubic capacity of the radiator is increased as comparedwith the ratio of area to capacity in a radiator using tubes of circularcross-section.

Figs. 11 and 11a illustrate another method of bending the cooling tubesto form a radiator of substantially the same frontal outline as thatshown in Fig. 4. In this arrangement, the two legs of each cooling tube,instead of being curved oppositely as are the portions b of the tubeshown in Fig. 5, are curved in the same direction, the portion 0 of thetube being in the nature of a return bend and the two legs of the tube,when the tube is secured in position in the radiator being axially inalignment. In Fig. 11 only one set or series of tubes is shown, but itwill be evident that with this arrangement a plurality of series oftubes may be employed as in the arrangement shown in Fig. 4 and it willfurther be evident that where a plurality of series of tubes isemployed, the tubes in different series may be curved in oppositedirections rotationallyso as to cross each other when viewed frontallyof the radiator. In

order to support the cooling tubes against vibration, the outer portionsof the tubes may be advantageously connected by means of a circular band86 secured to the tubes in any desired manner, but preferably weldedthereto by means of spot welds 88.

In Figs. 12 to 18 inclusive, there is illustrated the successive stepsof manufacture of a form of tube of flattened cross-section having thegen eral shape of the tubes shown in Figs. 4 to 6. In making this formof tube a plain cylindrical tubular steel blank 90 is drawn at its endsto provide end portions 92 and 94 of circular cross-section and ofreduced diameter as shown in Fig. 13. The drawing of the end portionsincreases the length of the tube somewhat and the tube is then bent atits central part to provide two similar and axially offset portions. Asshown in Fig. 14, this bending operation reduces the length of the tubeto substantially its original length and the portion of the tubeintermediate the ends 92 and 94 is then flattened to provide a tube theshape of which in plan and elevation is as shown in Figs. 15 and 16. Thetube is then bent into loop form and the ends rolled into the centralcasing 22, as shown in Figs. 18 and 19.

In Figs. 20 to 22, a radiator arrangement employing tubes of the formjust described is shown, the radiator illustrated comprising but oneseries or set of tubes. As shown in Fig. 22, the tube structure isadvantageously stiffened and held against vibration by spot welding theouter portions of adjacent tubes together as indicated at 96. It will beevident that any suitable arrangement for bracing the outer portions ofthe tubes, such, for example, as the means shown in Figs. 11 or 22 maybe employed in the form of radiator construction shown in Figs. 1 and 4.

In Figs. 23 and 24 is illustrated another form of apparatus embodyingthe invention and adapted to be employed with an aviation engine. In theexample illustrated, the engine, indicated generally at 100, is of theradial type, one cylinder thereof being shown at 112. The cylinders areprovided with the usual cooling jackets which are each connected bymeans of suitable passages to the conduit 136 leading to the inlet sideof the circulating pump member 160 situated in the inlet chamber 124formed by the central casing 122 of the radiator. Casing 122 alsoprovides a central outlet chamber 126 from which the outlet conduit 138supplies cooling fluid to the jackets of the several cylinders by meansof suitable connections, not shown.

The central casing 122 of the radiator is, in this instance, arrangedaround the crank shaft 102 which constitutes the main shaft of theengine and which extends through the casing 122 in the same manner asdoes the shaft 46 in the arrangement shown in Fig. 1. The pump member160 is fixed to the main shaft 102 of the engine. This shaft may also beconsidered as the propeller shaft and the projecting end provides asuitable mounting for the propeller 104 which in addition to its primaryfunction as a propeller, also acts as and may be considered as a coolingfan for the radiator.

In the example illustrated, the cooling tubes comprise a single set orseries 128 and it will be evident that more tubes may be employed ifdesired. It will further be evident that any of the several specificforms and arrangements of tubes, hereinbefore described, and others, may

be employed. It is also to be noted that in this is radially outside oftheinlet chamber rather than axially to one side thereof. Thisarrangement provides an axially compact radiator and it will be evidentthat the arrangement shown in this figure or the arrangement shown inFig. 1 may be used in accordance with the requirements for any givenengine design.

As will be evident from Figs. 23 and 24, the radiator and pump comprisea single unitary assembly connected to the engine by means of conduits136 and 138 and removable therefrom as a unit upon disconnection ofthese conduits from the engine and removal of the propeller from the endof shaft 102. .1

In case the engine is of the type in which the propeller is mounted on aseparate shaft geared to the crank shaft of the engine, the radiatorcasing 122 is preferably mounted on the separate propeller shaft so thatits relation to the propeller will be as shown in Fig. 23.

The present'invention is of particular advantage in connection withaviation motors since the relatively small amount of radiating surfacerequired and the arrangement thereof according to the invention providesa radiator giving minimum air resistance and in this connection it is tobe noted that this characteristic of the invention makes favorable itsuse with aviation engines of the in-line type as well as with engines ofthe radial type.

It will be apparent to those skilled in the art that many changes andvariations may be made in the specific form of apparatus for carryingthe invention into effect without departing from the spirit or scope ofthe invention as defined in the appended claims, in connection withwhich, I wish to point out that the term oil as therein employed is tobe considered generically as embracing fluids other than lubricating oilbut having the same general characteristics as lubricating oil withrespect to cooling properties, that the term closed circuit coolingsystem as therein employed is to be understood as embracing, but withoutlimitation, systems such as that shown in my copending applicationSerial No. 661,250, hereinbefore referred to, in which provision is madefor release of fluid from the closed circuit and for the introduction tothe circuit of fluid to replacelosses due to leakage or other causes,and that the term positive circulation as therein employed, is not to beconsidered as limited in sense to positive displacement but is to beconsidered as including all types of systems in which circulation iseffected by mechanical means in contradistinction to the so-calledthermo-siphon circulation.

What I claim is:

1. In a closed circuit cooling system for internal combustion engines, aunitary assembly comprising a radiator, a cooling fan, a pump forcirculating cooling fluid and. means for driving the fan and pump, saidassembly being adapted to be secured to and to be removed from an engineas a single unit.

2. In a closed circuit cooling system for ining tubes connecting saidchambers and. extending outwardly therefrom, a cooling fan adjacent tosaid radiator, a pump for circulating cooling fluid through theradiator, means for driving said fan and said pump and inlet and outletconduits for conducting cooling fluid to and from said radiator, saidradiator, said fan, said pump and said driving means comprising aunitary assembly and said inlet and outlet conduits providing means forsupporting said assembly from an engine.

4. In apparatus of the character described, the combination with aninternal combustion engine having spaces for circulation of coolingfluid in a closed circuit, of a radiator comprising inlet and outletchambers and bent cooling tubes connecting said chambers and inlet andoutlet conduits connecting said chambers and said spaces, said radiatorbeing supported by said conduits at the forward end of the engine.

5. In apparatus of the character described, the combination with aninternal combustion engine having spaces for circulation of coolingfluid in a closed circuit and having a main shaft, of a radiatorcomprising central inlet and outlet chambers and bent cooling tubesconnecting said chambers and extending outwardly therefrom and conduitsfor connecting said chambers with said spaces, said chambers and coolingtubes being arranged around said shaft.

6. Apparatus of the character described comprising, in combination, aninternal combustion engine including cylinders having spaces forcirculation of cooling fluid in a closed circuit and a main shaftextending laterally of said cylinders, a propeller mounted on saidshaft, a radiator located between the engine cylinders and the propellercomprising inlet and outlet chambers around said shaft and bent coolingtubes connecting said chambers and extending outwardly therefrom andconduits connecting said chambers and said spaces for circulation ofcooling fluid in a closed path of flow.

7. In apparatus of the character described, in combination, a radiatorcomprising central inlet and outlet chambers, a plurality of coolingtubes connecting said chambers and extending out wardly therefrom, saidtubes being bent to provide a radiator of substantially circular frontal,form, a cooling fan mounted for rotation coaxially with the axis of theradiator and conduits for supplying cooling fluid to and withdrawingcooling fluid from said chambers.

8. In apparatus of the character described, in combination, a casingproviding central inlet and outlet chambers, a plurality of bent coolingtubes connecting said chambers and extending outwardly therefrom, arotatably mounted shaft extending through said casing centrally thereof,a

cooling fan mounted on one projecting end of said shaft, a centrifugalpump for circulating cooling fluid through said tubes mounted on saidshaft within said casing and means for driving said shaft.

9. In apparatusof the character described, in combination, a casingproviding central inlet and outlet chambers, a plurality of bent coolingtubes connecting said chambers and extending outwardly therefrom, arotatably mounted shaft extending through said casing centrally thereof,a cooling fan mounted on one projecting end of said shaft, a centrifugalpump for circulating cooling fluid through said tubes mounted onsaidshaft within said casing and a pulley for driving said shaft mounted onthe other projecting end thereof.

10. In apparatus of the character described, in combination, a casingproviding central inlet and outlet chambers, a plurality of bent coolingtubes connecting said chambers and extending outwardly therefrom, arotatably mounted shaft extending through said casing centrally thereof,a pump for circulating cooling fluid through said tubes mounted on saidshaft within said casing, spring loaded packing means between said shaftand said casing at either side of said pump and means mounted on aprojecting end of said shaft for driving the same. v

11. In apparatus of the character described, in combination, a casingproviding central inlet and outlet chambers, 'a plurality of bentcooling tubes connecting said chambers and extending outwardlytherefrom, a rotatably mounted shaft ex-' tending through said casingcentrally thereof, a pump for circulating cooling fluid through saidtubes mounted on said shaft within said casing, spring loaded packingmeans between said shaft and said casing at either side of said pump, apulley mounted on one projecting end of said shaft for driving the sameand a cooling fan mounted on the other projecting end of the shaft.

12. In apparatus of the characterdescribed, in combination, a casingproviding central inlet and outlet chambers, said chambers beingarranged axially side by side, a plurality of bent cooling tubesconnecting said chambers and extending outwardly therefrom, a shaftrotatably mounted in said casing centrally thereof, a centrifugalpumpfor circulating cooling fluid through said tubes mounted on saidshaft within the inlet chamber and a plurality of difiusors between theoutlet of said pump and the inlet ends of said cooling tubes.

13. In apparatus of the character described, in combination, a casingproviding central inlet and outlet chambers, said chambers beingarranged axially side by side, a plurality of cooling tubes connectingsaid chambers, a shaft rotatably mounted in said casing centrallythereof, a pump mounted on said shaft within said casing for causingcirculation of cooling fluid through said tubes, said pump being locatedin one of said chambers and a by-pass providing for direct flow ofcooling fluid from one to the other of said chambers.

14. In apparatus of the character described, in combination, a casingproviding central inlet and outlet chambers, said chambers beingarranged axially side by side, a plurality of cooling tubes connectingsaid chambers, a shaft rotatably mounted in said casing centrallythereof, a centrifugal pump for circulating cooling fluid through saidtubes mounted on said shaft within said inlet chamber, a ring ofdiffusor blades located in the inlet chamber between the outlet of thepump and the inlet ends of said tubes and a by-pass opening providing adirect connection between said inlet chamber outwardly of said ring ofdifiusor blades and said outlet chamber.

15. In apparatus of the character described, in combination, a casingproviding central inlet and outlet chambers, a plurality of bent coolingtubes connecting said chambers and extending outwardly therefrom, acentral rotatably mounted shaft extending through the axially oppositesides of said casing, a cooling fan mounted on one projecting end ofsaid shaft and a driving pulley mounted on the other projecting end ofsaid shaft.

16. A positive circulation, closed circuit, oil

cooling system for internal combustion engines comprising a radiatorhaving central inlet and outlet chambers and a plurality of bent coolingtubes connecting said chambers and extending outwardly therefrom.

17. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers, said chambers being in the form of bodies ofrevolution and having a common axis, and a plurality of bent coolingtubes connecting said chambers and extending outwardly therefrom.

18. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprisinga radiator having central inletand outlet chambers and aplurality of bent cooling tubes connecting saidchambers and extending outwardly therefrom, said tubes being arranged sothat the frontal area occupied by the radiator is substantially that ofa body of revolution.

19. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having centralcircular inlet and outlet chambers arranged on a common axis and aplurality of bent cooling tubes connecting said chambers and extendingoutwardly therefrom, said tubes being arranged so that the frontal areaof the radiator is substantially that of a circle concentric withrespect to said axis.

20. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having centralinlet.and outlet chambers in the form of bodies of revolution having acommon axis and a plurality of bent cooling tubes connecting saidchambers and extending outwardly therefrom, the ends of said tubes beingarranged in a plurality of planes normal to said axis.

21. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers in the form of bodies of revolution having a commonaxis and a plurality of bent cooling tubes connecting said chambers andextending outwardly therefrom, the ends of said tubes being arranged ina plurality of planes normal to said axis and the inlet and outlet endsof any given tube being situated in different ones of said planes andspaced peripherally of said chambers.

22. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers and a plurality of bent cooling tubes connectingsaid chambers and extending outwardly therefrom, said tubes comprisingportions situated in planes normal to the central axis of the radiator.

23. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers and a plurality of bent cooling tubes connectingsaid chambers and extending outwardly therefrom, said tubes comprisinginvolute curved portions situated in planes normal to the central axisof the radiator and said tubes being circumferentially spaced withrespect to each other uniformly around said central chambers, saidinvolute curved portions providing interstices of substantially uniformarea for flow of air axially of the radiator between adjacent tubes.

24. A positive circulation, closed circuit, oil v cooling system forinternal combustion engines ii} comprising a radiator having centralinlet and outlet chambers and a plurality of bent cooling tubesconnecting said chambersand extending outwardly therefrom in the form ofloops, the legs of the loops being located in axially spaced planesnormal to the axis of the radiator and being curved in oppositedirections in adjacent planes.

25. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers and a plurality of bent cooling tubes connectingsaid chambers and extending outwardly therefrom, each of said tubescomprising axially spaced legs connected by a return bend tube portion,said legs being curved circumferentially of the radiator and the legs ofeach tube being in axial alignment with respect to each other.

26. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers and a plurality of bent cooling tubes connectingsaid chambers and extending outwardly therefrom, each of said tubescomprising axially spaced legs connected by a return bend tube portion,said legs being of involute curved form in planes normal to the axis ofthe radiator and the legs of each of said tubes being in axial alignmentwith respect to each other.

2'7. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers and a plurality of bent cooling tubes connectingsaid chambers and extending outwardly therefrom, each of said tubesbeing in the form of a loop and means for joining adjacent tubesoutwardly of said chambers to provide a relatively rigid tube structure.

28. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers and a plurality of bent cooling tubes connectingsaid chambers and extending outwardly therefrom, each of said tubescomprising two curved legs opposite with respect to each other axiallyof the radiator and located in planes normal to the axis of theradiator, the outer ends of said legs being connected by a tube portionoblique with respect to the axis of the radiator and the inner ends ofsaid legs joining the walls of said chambers radially.

29. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers and a plurality of bent cooling tubes connectingsaid chambers and extending outwardly therefrom, each of said tubesbeing flattened intermediate its ends so that the flattened portionsextend axially of the radiator.

30. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers and a plurality of bent cooling tubes connectingsaid chambers and extending outwardly therefrom, said tubes being ofirregular cross-section intermediate their ends to produce turbulentflow of cooling fluid therethrough.

31. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers and a plurality of bent cooling tubes connectingsaid chambers and extending outwardly therefrom, said tubes beingflattened at intervals along their lengths to produce tur -bulent flowof cooling fluid therethrough.

32. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers, a plurality of bent cooling tubes connecting saidchambers and extending outwardly therefrom and means in said tubes forproducing turbulent flow of cooling fluid therethrough.

33. A positive circulation, closed circuit, oil cooling system forinternal combustion engines comprising a radiator having central inletand outlet chambers, a plurality of bent cooling tubes connecting saidchambers and extending outwardly therefrom, and means in. said tubes forproducing turbulent flow of cooling fluid therethrough, said meanscomprising corrugated metal strips within the tubes.

34. In a closed circuit cooling system for internal combustion engines,a unitary assembly adapted to be rigidly secured to a cylinder block ofthe engine and to project therefrom comprising a radiator having centralcasing structure providing inlet and outlet headers for cooling fluidand a plurality of cooling tubes connecting said headers, a centralshaft extending through said headers and projecting at axially oppositesides thereof, a fan for forcing air over said tubes mounted on one ofthe projecting ends of said shaft, means for rotating the shaft mountedon the other projecting end of the shaft, a pump impeller located withinsaid casing structure for forcing cooling fluid into said cooling tubes,and inlet and outlet conduits for connecting said casing structure tothe cylinder block of an engine.

35. In a closed circuit cooling system for internal combustion engines,a unitary assembly adapted to be rigidly secured to a cylinder block ofthe engine and to project therefrom comprising a radiator having centralcasing structure providing inlet and outlet headers for cooling fluidand a plurality of cooling tubes connecting said headers, a centralshaft extending through said headers and projecting at axially oppositesides thereof, a fan for forcing air over said tubes mounted on one ofthe projecting ends of said shaft, means for rotating the shaft mountedon the other projecting end of the shaft, a pump impeller located withinsaid casing structure for forcing cooling fluid into said cooling tubes,and rigid inlet and outlet conduits for connecting said casing structureto the cylinder block of an engine, said conduits projecting ingenerally axial direction from said casing structure and having flangedends adapted to be bolted to correspondingly flanged portions of thecylinder block of an engine.

36. In a closed circuit cooling system for internal combustion engines,a unitary assembly adapted to be rigidly secured to a cylinder block ofthe engine and to project therefrom comprising a radiator having centralcasing structure providing inlet and outlet headers for cooling fluidand a plurality of bent cooling tubes connecting said headers andprojecting therefrom in the form of loops, said tubes being arranged toprovide a radiator having a generally circular frontal area, a centralshaft passing through said casing structure and projecting at each endthereof, a fan mounted on one of the projecting ends of said shaft andhaving a plurality of propeller type blades for forcing air axiallyacross said tubes, a pulley for rotating said shaft mounted on the otherprojecting end thereof, a pump impeller located in said central casingstructure for forcing cooling fluid through the inlet headers to theinlet ends of said tubes, and means providing inlet and outlet conduitsfor cooling fluid projecting from the side of said casing structure andembracing said pulley, said means including flanges at the ends of theconduits for detachably securing said assembly to the cylinder block 01'an engine.

37. In a closed circuit cooling system for internal combustion engines,a unitary assembly adapted to be rigidly secured to a cylinder block ofthe engine and to project therefrom comprising a radiator having centralcasing structure providing inlet and outlet headers for cooling fluidand a plurality of cooling-tubes connecting said headers, said headershaving circular outer walls and said tubes being bent to form loops withthe ends of the tubes projecting radially from the circular walls of theheaders, a central shaft rotatably mounted in said casing structure andpassing through the end walls thereof, a pump impeller on said shaft forforcing cooling fluid from the inlet headers into said cooling tubes, afan mounted on one projecting end of said shaft comprising propellerblades for forcing air axially across said cooling tubes, a pulleymounted on the opposite projecting end of said shaft, shaft packingmeans between the pump impeller and said fan, shaft packing meansbetween said pump impeller and said pulley, and means forming a part ofsaid central casing structure extending in generally axial directionfrom said headers past said fan to provide rigid support for saidassembly, said means providing inlet and outlet conduits for conductingfluid to and from the radiator and the ends of said conduits beingflanged to provide for detachable connection of the conduits with thecylinder block of an engine.

FREDRIK LJUNGSTRijM.

